The exhaust gas discharged from the internal combustion engine in vehicles such as truck or bus, or construction vehicles contains particulates harmfully exerting upon environment and human body. For this end, there are recently studied techniques for collecting and removing the particulates from the exhaust gas. As an example of such techniques is developed a ceramic honeycomb filer for the purification of the exhaust gas in order to collect and remove the particulates from the exhaust gas.
As a typical structure of this ceramic honeycomb structural body, as shown in FIG. 1A, there is mentioned a ceramic honeycomb structural body 10 formed by combining a plurality of pillar-shaped porous ceramic members (units) 11 through sealing material layers 14 to form a ceramic block and covering an outer periphery of the ceramic block with a sealing material layer 16 for preventing the leakage of the exhaust gas. As illustrated, the ceramic honeycomb structural body 10 takes a sectional form of circle, oval or polygon by bundling a plurality of ceramic members 11 each having a pillar-shaped structure as one constitutional unit. In the ceramic members 11, many cells 12 as a path for the exhaust gas are arranged in parallel to each other in longitudinal direction through cell walls 13. When the cells 12 are used as a filter, the end faces of them are alternately sealed with a plugging 15. When the exhaust gas passes through the cell walls 13, the particulates are collected by the cell walls 13, and hence the ceramic honeycomb structural body functions as a filter for the purification of the exhaust gas.
As a method of manufacturing the above ceramic honeycomb structural body is proposed a technique disclosed in Japanese unexamined patent publication No. H08-281036 (JP-A-H08-281036). This technique is a method wherein 100 parts by volume of silicon carbide powders having a mean particle size of 5 to 50 μm and a particle size ratio (D10/D50) of particle size with an oversize of 10% (based on mass) (D10) to particle size with an oversize of 50% (based on mass) of 0.2 or more in cumulative volume mean diameter MV (mean volume diameter) of particle size distribution and added with 10% or less by volume of a sintering aid is compounded with 15 to 25 parts by volume of a pore forming agent having a mean particle size of 40 to 100 μm and molded and fired in a non-oxidizing atmosphere at 1600° C. or more to form a honeycomb structural body.
The contents of JP-A-H08-281036 are incorporated herein by reference in its entirety.